1. Technical Field
The present invention relates to electrothermal materials, and especially to flexible electrothermal composites containing carbon nanotubes.
2. Discussion of Related Art
Electrothermal materials can generate heat when a voltage is applied thereto. Usually electrothermal materials are made of metal, for example, tungsten filament. Metals have good conductivity which means they can generate a lot of heat even when a low voltage is applied, but such metals cannot be used in low temperature applications. Furthermore, most metals are rigid thus an electrothermal material that is made of a metal cannot vary its shape to fit the shape of an object that is contact with the electrothermal material. Both high resistance and high flexibility are needed in some applications such as for seat warmers, electric blankets, heated belts, immersion suits etc. Obviously, electrothermal materials that are made of metals don't meet this need.
In order to solve the aforementioned problem, an electrothermal material comprised of a polymer and a number conductive particles dispersed therein has been developed. The conductive particles can include metal powder or graphite powder. This type of electrothermal material has a relatively high flexibility and high resistance. However, in order to reach to an appropriate conductivity, a large amount of conductive particles need to be mixed with the electrothermal material. This inevitably significantly lowers mechanical strength of the electrothermal material. In addition, the lifetime of the electrothermal materials is reduced accordingly.
Therefore, there is a desire to develop an electrothermal material that has high flexibility, high resistance and high strength.